Ok, here is how I got that integrator initial condition.
First I added Trim Output Constraint on the "height" signal. To do that, right click on the signal, and specify Trim Output Constraint, as shown below.
Next, launch Linear Analysis Tool:
Now, we want to trim the model:
Click to specify the trim conditions:
All states should be in steady state:
The output (height) should be at 0:
Click "trim". Tool computes the operating condition op_trim1. Examine it to see the value for Integrator in the PID Controller:
All of this can also be done with a few lines of code:
model = 'Proba_3';
opspec = operspec(model);
opspec.Outputs(1).Known = true;